Physical Science Practice Questions — Armed Services Vocational Aptitude Battery (ASVAB) — Page 12

Question 221Question →

A maintenance cart with a mass of $250\text{ kg}$ travels along a straight horizontal track. If the cart uniformly slows down from an initial velocity of $15\text{ m/s}$ due east to $5\text{ m/s}$ due east over a time interval of $5\text{ seconds}$ , what is the magnitude and direction of the net force acting on the cart?

500\text{ N}

directed due east

500\text{ N}

directed due west

4{}900\text{ N}

directed due west

0.5\text{ N}

directed due west

Show answer & explanation

Answer: $500\text{ N}$ directed due west

Answer

The magnitude of the net force is

500\text{ N}

, directed due west.

Acceleration is the change in velocity divided by time:

a = (5\text{ m/s} - 15\text{ m/s}) / 5\text{ s} = -2\text{ m/s}^2

. The negative sign indicates an acceleration directed due west (opposite to the eastward motion). Applying Newton's Second Law (

F = ma

), the net force is

250\text{ kg} \times 2\text{ m/s}^2 = 500\text{ N}

directed due west.

Step-by-Step Solution

1

Calculate the acceleration using the kinematics formula

a = \frac{v_f - v_i}{\Delta t}

.

a = \frac{5\text{ m/s} - 15\text{ m/s}}{5\text{ s}} = \frac{-10\text{ m/s}}{5\text{ s}} = -2\text{ m/s}^2

(or

2\text{ m/s}^2

directed west).

Acceleration is the rate of change of velocity over time.

2

Calculate the magnitude and direction of the net force using Newton's Second Law,

F_{\text{net}} = m \cdot a

.

F_{\text{net}} = 250\text{ kg} \times 2\text{ m/s}^2 = 500\text{ N}

directed west.

Net force is equal to mass multiplied by acceleration and always points in the same direction as the acceleration vector.

Key Concept

Newton's Second Law of Motion (

F_{\text{net}} = ma

) and Kinematics of Linear Deceleration

Alternative Method

Use the impulse-momentum theorem (

F_{\text{net}} \cdot \Delta t = m \cdot \Delta v

). Here,

\Delta p = 250\text{ kg} \times (5\text{ m/s} - 15\text{ m/s}) = -2{}500\text{ kg}\cdot\text{m/s}

. Dividing momentum change by

\Delta t = 5\text{ s}

yields

F_{\text{net}} = -500\text{ N}

, meaning

500\text{ N}

directed west.

Estimated Time:1m 0s

Question 222Question →

An electric toaster toasts bread using glowing heating coils placed a short distance away from the slices without touching them. Which method of heat transfer is primarily responsible for warming and toasting the bread?

Conduction

Convection

Radiation

Condensation

Show answer & explanation

Answer: Radiation

Answer

Radiation transfers thermal energy across the space between the coils and the bread via electromagnetic infrared waves.

Thermal radiation transfers energy via electromagnetic waves, such as infrared light. Because the bread does not touch the glowing wires, radiation is the primary mechanism heating the surface of the bread directly across the gap.

Step-by-Step Solution

1

Analyze the physical arrangement in the toaster.

The bread is placed near the glowing elements across an air gap without making direct physical contact.

Determining whether physical contact occurs narrows down the possible heat transfer mechanisms.

2

Identify the primary mechanism of heat transfer through empty space and transparent air.

The glowing heating elements emit electromagnetic energy in the form of infrared radiation directly onto the bread's surface.

Thermal radiation does not require direct contact or fluid circulation currents to transfer energy.

Key Concept

Thermal radiation transfers heat through electromagnetic waves without requiring direct contact or a circulating medium.

Estimated Time:45s

Question 223Question →

A $12\text{ V}$ direct-current car battery is connected to a circuit powering a single headlight with a resistance of $4\,\Omega$ . What is the electric current, in amperes, flowing through the headlight?

Show answer & explanation

Answer: 3

Answer

The electric current flowing through the headlight is 3 amperes.

According to Ohm's law, electric current (

I

) equals voltage (

V

) divided by resistance (

R

). Dividing a voltage of

12\text{ V}

by a resistance of

4\,\Omega

yields an electric current of

3\text{ A}

.

Step-by-Step Solution

1

Identify the relationship between voltage, current, and resistance using Ohm's law.

V = I \times R

, which rearranges to

I = \frac{V}{R}

.

Ohm's law governs the relationship between electric potential difference, current flow, and resistance in a DC circuit.

2

Substitute the given values into the formula and solve for current.

I = \frac{12\text{ V}}{4\,\Omega} = 3\text{ A}

Dividing the electromotive force (voltage) by the total circuit resistance yields the resulting electric current.

Key Concept

Ohm's Law (

V = IR

)

Question 224Question →

In classical mechanics, fundamental laws and principles define how forces govern the motion and interaction of physical bodies. Match each mechanical principle with its correct scientific definition or governing rule.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Newton's First Law pairs with the statement describing an object maintaining constant velocity unless acted upon by a net force; Newton's Second Law pairs with the statement that acceleration is directly proportional to net force and inversely proportional to mass; Newton's Third Law pairs with the statement regarding equal and opposite force interactions between two bodies; and the Law of Conservation of Momentum pairs with the statement that total mass times velocity remains constant in a closed system.

Each mechanical principle aligns directly with its formal physical definition: Newton's First Law governs inertia and zero-acceleration states; Newton's Second Law defines how net force produces acceleration proportional to force and inversely proportional to mass; Newton's Third Law defines equal and opposite force pairs between interacting bodies; and the Law of Conservation of Momentum dictates the invariance of total system momentum in closed systems.

Step-by-Step Solution

1

Identify the foundational definition of inertia and unaccelerated motion.

Newton's First Law matches the description of objects maintaining rest or uniform straight-line motion unless a net external force intervenes.

Inertia requires zero net force for constant velocity.

2

Identify the quantitative relationship governing net force, acceleration, and mass.

Newton's Second Law matches the relationship where acceleration is proportional to net force and inversely proportional to mass (

F_{\text{net}} = ma

).

This law provides the direct causal formula for changing an object's velocity.

3

Identify the law governing reciprocal force pairs between interacting objects.

Newton's Third Law matches the statement of equal and opposite forces acting simultaneously on two separate bodies.

Forces in nature always exist in matched action-reaction pairs across interacting bodies.

4

Identify the principle governing total quantity of motion across collisions in isolated systems.

The Law of Conservation of Momentum matches the constant total vector product of mass and velocity (

mv

) in closed systems.

Internal interaction forces cancel out vectorially across the entire system, preserving total momentum.

Key Concept

Fundamental Principles and Governing Laws of Classical Mechanics

Estimated Time:1m 0s

Question 225Question →

A solid rectangular block of an unknown metal has dimensions of $5\text{ cm}$ in length, $4\text{ cm}$ in width, and $2\text{ cm}$ in height. If the total mass of the block is $316\text{ g}$ , what is the density of the metal in $\text{g/cm}^3$ ?

Show answer & explanation

Answer: 7.9

Answer

The density of the metal block is

7.9\text{ g/cm}^3

.

Density measures mass per unit volume (

D = \frac{m}{V}

). The volume of the rectangular prism is calculated by multiplying its dimensions (

5\text{ cm} \times 4\text{ cm} \times 2\text{ cm} = 40\text{ cm}^3

). Dividing the mass (

316\text{ g}

) by this volume (

40\text{ cm}^3

) yields

7.9\text{ g/cm}^3

.

Step-by-Step Solution

1

Calculate the volume of the rectangular metal block from its dimensions.

V = 5\text{ cm} \times 4\text{ cm} \times 2\text{ cm} = 40\text{ cm}^3

To determine density, the total volume must first be calculated from the given geometric measurements.

2

Divide the mass of the block by its calculated volume.

\text{Density} = \frac{316\text{ g}}{40\text{ cm}^3} = 7.9\text{ g/cm}^3

Density is defined as mass per unit volume (

D = \frac{m}{V}

).

Key Concept

Density is a characteristic physical property of matter defined as mass divided by volume (

D = \frac{m}{V}

).

Estimated Time:1m 0s

Question 226Question →

The periodic table organizes chemical elements into vertical columns known as groups or families, where members share similar valence electron configurations and chemical behaviors. Match each periodic table group on the left with its defining chemical characteristic on the right.

Click a left item, then click its matching right item

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Answer

Alkali Metals match with having 1 valence electron and reacting vigorously with water; Alkaline Earth Metals match with having 2 valence electrons and forming

+2

cations; Halogens match with having 7 valence electrons and forming salts; Noble Gases match with possessing a complete valence shell and extreme chemical inertness.

The periodic table organizes elements by valence electron configurations. Group 1 elements (Alkali Metals) have 1 valence electron and react vigorously with water. Group 2 elements (Alkaline Earth Metals) have 2 valence electrons and form

+2

cations. Group 17 elements (Halogens) have 7 valence electrons and readily gain an electron to form salts. Group 18 elements (Noble Gases) have complete valence shells, making them chemically inert.

Step-by-Step Solution

1

Determine valence electron count and characteristic reactivity for Group 1 elements.

Group 1 elements (Alkali Metals) have 1 valence electron and react violently with water.

The single outermost electron is readily lost, forming

+1

cations.

2

Determine valence electron count and ion formation for Group 2 elements.

Group 2 elements (Alkaline Earth Metals) have 2 valence electrons and form

+2

cations.

Losing two electrons achieves a stable preceding noble gas electron configuration.

3

Determine valence electron count and bonding behavior for Group 17 elements.

Group 17 elements (Halogens) have 7 valence electrons and readily gain 1 electron to form salts.

Gaining a single electron completes the outer valence octet.

4

Determine valence shell status and reactivity for Group 18 elements.

Group 18 elements (Noble Gases) possess full outer electron shells and are chemically inert.

A full complement of valence electrons provides maximum thermodynamic and chemical stability.

Key Concept

Periodic Table Groups and Valence Electron Trends

Question 227Question →

An isotope of titanium has a mass number of $48$ and contains $26$ neutrons in its nucleus. How many electrons surround the nucleus of a neutral atom of this isotope?

74

22

26

48

Show answer & explanation

Answer: $22$

Answer

A neutral atom of this titanium isotope has

22

electrons.

The mass number (

A = 48

) is the total count of protons and neutrons in the nucleus. Subtracting the

26

neutrons from the mass number gives

22

protons (

48 - 26 = 22

). In a neutral atom, the number of electrons equals the number of protons, meaning there are

22

electrons orbiting the nucleus.

Step-by-Step Solution

1

Calculate the number of protons in the nucleus using the mass number and neutron count

Number of protons

= 48 - 26 = 22

The mass number (

A

) equals the sum of protons (

Z

) and neutrons (

N

), so

Z = A - N

.

2

Determine the number of electrons in the electrically neutral atom

Number of electrons

= 22

In any neutral atom, the number of negatively charged electrons equals the number of positively charged protons.

Key Concept

Relationship between mass number, subatomic particles, and atomic neutrality

Estimated Time:45s

Question 228Question →

Match each fundamental atomic structure concept with its correct scientific definition.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Atomic number pairs with the proton quantity determining elemental identity; Mass number pairs with the sum of protons and neutrons; Isotopes pair with atoms having identical protons but different neutrons; Valence electrons pair with outermost electrons governing chemical reactivity.

Each term accurately describes a foundational property of atomic architecture: the atomic number corresponds strictly to proton count, mass number equals protons plus neutrons, isotopes are variants differing in neutron count, and valence electrons occupy the outermost shell to drive chemical behavior.

Step-by-Step Solution

1

Identify the definition of atomic number

Matched with the number of protons that defines the element (

Z

)

Every neutral or ionized atom of an element always contains the same characteristic number of protons.

2

Identify the definition of mass number

Matched with the sum of nuclear particles (protons + neutrons)

Electrons have negligible mass compared to nucleons, so atomic mass number is the total count of protons and neutrons.

3

Identify the definition of isotopes

Matched with atoms of the same element containing differing neutron quantities

Because atomic number remains constant for a given element, variations in atomic mass within an element arise solely from neutron count.

4

Identify the definition of valence electrons

Matched with the outermost electrons governing bonding behavior

The electron configuration in the highest energy level dictates how an atom interacts and shares or transfers electrons during reactions.

Key Concept

Core atomic structure parameters, subatomic particle arrangements, and isotopic terminology

Estimated Time:1m 0s

Question 229Question →

Elements in the periodic table are organized into families based on recurring valence electron configurations and characteristic chemical properties. Match each periodic table group on the left with its defining valence configuration and reactivity property on the right.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Alkali metals (Group 1) match with having

1

valence electron and forming

+1

cations; Alkaline earth metals (Group 2) match with having

2

valence electrons and forming

+2

cations; Halogens (Group 17) match with having

7

valence electrons and forming

-1

anions; Noble gases (Group 18) match with having a complete outer electron shell and being chemically inert.

Each chemical family's behavior is dictated by its valence electron configuration: Group 1 has

1

valence electron forming

+1

ions; Group 2 has

2

valence electrons forming

+2

ions; Group 17 has

7

valence electrons gaining

1

electron to form

-1

ions; Group 18 has complete outer shells resulting in chemical inertness.

Step-by-Step Solution

1

Identify the valence electron count and typical ion formation for Group 1 (Alkali metals).

Group 1 elements have

1

valence electron and lose it easily to form

+1

cations.

Losing

1

electron gives alkali metals the stable electron configuration of the preceding noble gas.

2

Identify the valence electron count and typical ion formation for Group 2 (Alkaline earth metals).

Group 2 elements have

2

valence electrons and lose them to form

+2

cations.

Losing both valence electrons achieves a stable outer octet.

3

Identify the valence electron count and typical ion formation for Group 17 (Halogens).

Group 17 elements have

7

valence electrons and gain

1

electron to form

-1

anions.

Nonmetals with

7

valence electrons require only

1

additional electron to reach a full octet.

4

Identify the outer shell characteristics and reactivity of Group 18 (Noble gases).

Group 18 elements have completely filled valence shells and are non-reactive (inert).

A filled outer shell provides maximum thermodynamic stability without sharing, gaining, or losing electrons.

Key Concept

Periodic table groups reflect valence electron numbers that determine characteristic chemical properties and predictable ion formation.

Estimated Time:1m 0s

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